Destroyed collar

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The destroyed collar is a slave collar that has detonated, and can be used as a necklace of sorts that appears that the wearer attempted (and failed) to take it off, judging by the decapitated head and the nearby wrench.

It is obtained when you start the Brotherhood of Steel story line but is removed after the first quest you do for them. It can also be found on a corpse labeled "Man" in the westernmost corner of a ruined building at Freeside's East Gate near Jacob Hoff and across from Mick & Ralph's, which is part of the I Could Make You Care quest line, if choosing the rangefinder.

It leaves one to wonder how this particular collar did not completely explode. For instance in Fallout 3, the collars were un-lootable and could not even be seen on the corpse visually once they detonated.